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Method for identifying objects using data processing techniques

  • US 5,528,703 A
  • Filed: 01/10/1994
  • Issued: 06/18/1996
  • Est. Priority Date: 02/18/1992
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for creating a mask to identify objects of interest wherein the objects of interest are contained in an image represented by an array of image data, said method comprising the steps of:

  • (a) removing objects from the image that are larger than a predetermined size and performing a histogram to provide parameter data, wherein the parameter data comprises intensity ranges of background range, cytoplasm range and nucleus range, wherein the objects include a texture, and objects of interest have an intensity value within the nucleus range;

    (b) enhancing the image contrast by removing the texture of the objects of interest using morphological opening and conditional dilation on the image data to provide data representing a non-textured image wherein the texture of objects of interest is removed only from the image areas having the intensity value within the nucleus range;

    (c) normalizing the background of the image represented by the image data to decrease the difference in contrast between the background and the objects of interest to provide data representing a normalized image, wherein image data having an intensity value greater than a background threshold value is set to the background threshold value before normalizing;

    (d) combining the normalized image and the non-textured image by filtering the data representing the normalized image in a linear convolution and subtracting the data representing the non-textured image therefrom to provide data representing an enhanced image;

    (e) obtaining the difference between the non-textured image and the image to provide a textured image;

    (f) processing the data representing the non-textured image to create data representing a threshold image by performing a morphological dilation residue operation on the data representing the textured image and combining the data representing the textured image and the non-textured image with the result to create data representing a threshold image;

    (g) creating a low threshold image and a high threshold image by subtracting and adding, respectively, a predetermined offset from the data representing the threshold image;

    (h) comparing the data representing the threshold image with the data representing the enhanced image to identify objects of interest by identifying data representing an object of interest as any data representing the enhanced image having a value exceeding the value of the respective data representing the threshold image to create a preliminary mask;

    (i) processing the data representing the enhanced image to detect its dark edges, where a variation between a pixel and its neighbor represents the object of interest, and produce data thereof and combining said dark edge data with the preliminary mask to create data representing a dark edge incorporated mask;

    (j) processing the data representing the enhanced image to detect its bright edges, where a variation between a pixel and its neighbor represents the pixel outside the object of interest, and combining the resulting data with the dark edge incorporated mask to create data representing a bright edge excluded mask;

    (k) filling holes in the bright edge excluded mask by inverting the bright edge excluded mask and excluding data representing an object of size less than the predetermined size by a predetermined amount, the identified objects are then added back to the bright edge excluded mask to create a hole-filled mask;

    (l) eroding the hole-filled mask by a first amount, then dilating by a second amount less than the first amount and determining a separation boundary between the identified objects through morphological closing residue operation and then subtracting the separation boundary from the hole-filled mask to create an overlay object separated mask;

    (m) comparing the data representing the high threshold image with the enhanced image to create a data representing a high threshold mask, wherein a pixel including the data representing a high threshold mask is included in the high threshold mask if the data'"'"'s respective value in the enhanced image is greater than a respective data value of the high threshold image, and wherein any objects identified by the high threshold mask are added to the object separated mask by a set union operation to create a high threshold included mask;

    (n) comparing the data representing the low threshold image with the enhanced image to create a data representing a low threshold mask, wherein a pixel including the data representing a low threshold mask is included in the low threshold mask if the data'"'"'s respective value in the enhanced image is greater than a respective data value of the low threshold image; and

    (o) eroding the data representing the high threshold included mask by a small amount and dilating the resulting data by a large amount to connect all objects that are identified by the high threshold included mask and combining the resulting data with the low threshold mask to identify any objects in the low threshold mask not proximate the connected objects of the eroded and dilated high threshold included mask and adding these objects to the original high threshold included mask to create the mask identifying the objects of interest.

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